This article explains what options you have for charging and listening to your iPod in your car.
The CD player is becoming less and less popular as MP3 technology continues to get better. Personally I don't even own a CD, and why should I when I can carry all my music around in a device smaller than a CD. Yet I still see people with the classic CD binder shoved under a seat in their car and when they want to hear something they have to pull it out, flip through the pages, find the CD they want and put it in. That's too much work for me (plus its dangerous while driving). On the other hand a lot of people are very aware of technology and have had iPod adapters in their cars for years now. Yet most of the wireless transmitters made for the iPod are just that, transmitters. The transmitter attachments usually work fine (depending on the brand) but won't charge your iPod so it may run out of battery. Some of the devices also require you to download radio station transmission signals onto your iPod which takes up valuable space that could be used for music or videos.
Using an FM Trasmitter with a built in charger
Monster has several FM Transmitters for the iPod that both transmit your iPod songs onto your factory car stereo and charges the iPod at the same time. There are no downloads or setups involved you just plug in the adapter to your cars cigarette lighter or power supply, plug the other end into your iPod and enjoy your music. There are a few different options that Monster provides depending on your specific needs:

Monster iCarplay Plus FM Transmitter - this device performs the same function as the regular iCarplay FM Transmitter but gives you the option of using any FM station. This may come in handy when you are in an area that doesn't have many radio stations.

Monster iCarplay 200 FM Transmitter. This particular model can perform the same functionality as the other two but gives you the option of letting it auto-scan for the highest quality station to play your songs on. It will seek through each FM station and tell you on your iPod screen what station to tune to.

These are all good options to choose from and you can pretty much make your choice depending on the features you want.
Using a MP3 Auxiliary Input
If you are lucky enough to have bought a new car that has an MP3 plug-in port on your stereo, or have an after-market head unit that has a plug-in then all you need is the Monster Mobile MP3 connect cord. This cord will work with any MP3 player by simply plugging one end into the headphone slot and the other into your MP3 connection on your car stereo. You will then be able to listen to top quality sound at the push of the play button. When using the auxilary input, you will need to use a separate iPod Car Charger.
Using a Cassette Adapter
If you want to listen to your iPod using your in-dash cassette player, you will need the Monster® iCarPlay™ Cassette Adapter. The cassette adapter plugs into your iPod's headphone jack and then you insert the cassette adapter into your car's cassette player just as if you were listening to a cassette tape. When using the cassette adapter, you will need to use a separate iPod Car Charger.
These little gadgets are great for long trips or when you want to listen to your iPod on a short drive. It is much more convenient to carry around one small MP3 player than hundreds of CD's that are a pain to keep up with.